The benthic communities of the Snorre field in the Northern North Sea (61°30′ N 2°10′ E): 1. The distribution and structure of communities in undisturbed sediments

The fauna of the Snorre oil field is diverse and varies along a 40 m depth gradient across the area. Abundance and species richness increase with increasing depth but diversity is highest in the centre of the gradient. The communities present differ widely from those of the adjacent but shallower Statfjord, Gullfaks and Tordis Fields and from the major communities found throughout much of the northern North Sea, a fact attributable to the greater depth, finer sediments, higher sediment organic levels and position on the western slope of the Norwegian Trench. They have greater affinities with the communities in the Troll Field, 85 km SE on silt/clay sediments in the floor of the trench and the Heidrun Field, situated approximately 390 km N at similar depths and in an area of similar sedimentary composition. However the Snorre communities have a much higher number of suspension feeding and surface deposit feeding organisms than either of these other areas. This might be caused by higher current speeds in the Snorre area which could create favourable conditions for suspensivores. Such water movements might bring occasional incursions of intermediate Norwegian Sea water into the area. Indeed the Snorre fauna appears to bear some relationships to the intermediate depth faunas of the Norwegian Sea, and is clearly different from most of the better described northern North Sea faunas.     

海南石碌铁钴铜( 金) 矿床与 国内外IOCG 型矿床的对比研究

[摘 要] IOCG 矿床是近些年来被认知的一种重要矿床类型,因其巨大的经济和理论研究价值受到 国内外矿业界和学术界的重视。海南石碌铁钴铜(金)矿床在构造环境、与岩浆岩的关系、矿体特征、元 素和矿物组合、围岩蚀变等方面与国外典型的IOCG 矿床有相似之处。该矿床处于大陆边缘拉张的裂 谷环境,早期火山沉积岩为成矿提供初始矿源,后期侵入岩对成矿具有重要的改造富集作用,矿体基本 呈层状、似层状及少量脉状产于石碌群第六层中,一般铁矿体在上,钴铜矿体在下,具Fe-Cu-Co( -Au) 多元素组合,铁氧化物主要为赤铁矿,蚀变以透辉石化、透闪石化为主;在成矿时代方面区别于多数产在 元古宙的IOCG 矿床,而是经历了新元古代海相火山喷流沉积阶段、加里东期区域变质阶段、海西-印支 期热液改造阶段和燕山晚期热液改造阶段。文章认为石碌铁钴铜(金)矿床不仅与IOCG 矿床有较多相 似之处,与国内内蒙古白云鄂博铁稀土铌矿床、四川拉拉铜铁金钴钼稀土矿床、新疆乔夏哈拉铁铜金矿 床、云南迤纳厂铁铜稀土矿床和东川稀矿山铁铜矿床等也有相似之处。因此,在中国开展寻找IOCG 矿 床尤其是大型矿床,是很有前景的。     

Analytic hierarchy process approach for the selection of stream-gauging sites

ABSTRACT

This investigation proposes the use of the analytic hierarchy process (AHP) to evaluate potential sites for stream monitoring and broadcast of flood warnings. The methodology adopts variables established by the World Meteorological Organization (WMO) for the selection of stream-monitoring sites and incorporates new variables associated with the stream morphometry and hydraulics. The proposed approach quantifies subjective valuations through pairwise comparisons of judgements within the selection criteria. The uncertainty of expert judgement was assessed via Monte Carlo simulations and its effects on the resulting priority vector were analysed. This approach was applied on three main mountain watershed streams at which 11 alternative stream-gauging sites were evaluated and scored. According to our findings, six variables explain 0.711 of the total weight in the priority vector for the evaluation of a candidate site. Our approach is suitable for selecting the most stable alternative location based on a multi-criteria analysis in an inter-comparison arrangement.     

Capturing Farmers’ Knowledge: Testing the Analytic Hierarchy Process and a Ranking and Scoring Method

Abstract

Integrating local and Indigenous knowledge into land-use planning and the assessment of ecosystems services requires reliable, quantitative data. We tested two approaches to obtain such data by quantifying farmer opinion of different land-covers in Eastern Panama using (1) the analytic hierarchy process (AHP) and (2) a simpler ranking and scoring technique. Both methods produce a set of numerical values reflecting the ability of land-covers to deliver ecological and socio-economic criteria. We present our experience with both methods and offer recommendations for researchers looking to quantify landholder opinion. The AHP survey was relatively long (on average it took 19?min to complete per criterion) and we faced problems with inconsistent responses. In contrast, the ranking and scoring method was much quicker (only 3?min per criterion) and therefore may be more suitable for gathering more data from a larger number of farmers.     

The use of a paired comparison model in ordering stratigraphic events

Data from lowest and highest occurrence events in several stratigraphic sections are analyzed by means of a paired comparison model with ties. The model produces an estimated relative geochronological ordering of these events. This ordering must be compared with actual observations for revision and interpretation.     

Comparison of palynomorph assemblages from the Cretaceous/Tertiary boundary interval in Western Europe, northwest Africa and southeast China

The composition of palynomorph assemblages from selected sections through the Cretaceous/Tertiary (K/T) boundary interval in Western Europe, northwest Africa and China is discussed. Similarities are emphasised and widespread trends noted, including the evolutionary development of the porate group of pollen grains, palynomorph extinctions within the boundary interval, and links with a climatic cooling trend. The comparative analysis revealed numerous taxonomic and nomenclature problems, as a list of 71 forms recorded from five papers on European and North African topics demonstrates. These taxa are considered to be similar or identical to palynomorphs documented in four Chinese papers, despite the fact that almost all of the identifications differ at either generic or specific level, or both.     

Map Comparison or Traditional Mass-balance Measurements: Which Method is Better?

A number of Norwegian glaciers were selected in the 1960s for long-term mass-balance measurements, to produce necessary hydrological information for hydropower exploitation. Special large-scale glacier maps were produced for field work and data processing, and some glaciers have been mapped more than once. Thus, comparison of glacier maps can be used to calculate changes in glacier volume for some of the glaciers, provided they are of sufficient accuracy.
Conventional mass-balance measurements were carried out on all the selected glaciers. A cumulative calculation of net balances for a series of years is used to indicate the change in a glacier's volume during that period. However, various errors originate in the field, some of which are systematic, particularly on glaciers with large winter accumulation.
The present study indicates that certain errors are difficult to define and determine, For the maritime glacier Ålfotbreen, a cumulative mass-balance calculation gives a positive total balance (+3.4 m water equivalent in the period 1968–88), whereas the map comparison indicates a total negative balance (−5.8 m water equivalent). This indicates a discrepancy between the methods, which must be accounted for.
Determination of errors in mass-balance measurements is difficult. Sinking of stakes in the accumulation area and the use of sounding sticks (steel probes) in heavy snowlayers cause problems.     

A comparison of intertidal species richness and composition between Central California and Oahu,Hawaii

The intertidal zone of tropical islands is particularly poorly known. In contrast, temperate locations such as California's Monterey Bay are fairly well studied. However, even in these locations, studies have tended to focus on a few species or locations. Here we present the results of the first broadscale surveys of invertebrate, fish and algal species richness from a tropical island, Oahu, Hawaii, and a temperate mainland coast, Central California. Data were gathered through surveys of 10 sites in the early 1970s and again in the mid‐1990s in San Mateo and Santa Cruz counties, California, and of nine sites in 2001–2005 on Oahu. Surveys were conducted in a similar manner allowing for a comparison between Oahu and Central California and, for California, a comparison between time periods 24 years apart. We report a previously undocumented richness of intertidal species in both locations: 516 for Oahu and 801 for Central California. Surprisingly, when differences in search efforts are controlled, overall (alpha) diversity appears to be similar between locations, although site level (beta) diversity is much higher in California. Species richness in California generally increased along a wave exposure gradient and distance from an urban area. Much higher numbers of both invasive and endemic species were found on Oahu. In California, more invertebrate species were found in the 1990s, likely due to an improvement in taxonomic resources since the 1970s, and species composition was different in the two surveys due to the high incidence of rare species. Although some southern species increased in number between the two time periods and some northern species decreased, we detected little evidence of change favoring southern or northern species. These results are in line with recent findings that water temperatures in the Monterey Bay have been in a cooling trend since the 1980s, in contrast to many locations elsewhere in the world.     

Classification of boreal macrotidal littoral zone habitats in the Gulf of Maine: comparison of IKONOS and CASI multispectral imagery

Increasingly, remote sensing has become a useful tool for mapping and measuring terrestrial and aquatic environments. Advances in the spatial and spectral resolution of satellite-borne sensors have allowed affordable investigations of littoral macrotidal coastal systems that previously required more costly aircraft-based imagery. In this communication, we compare the results from analysis of a 4 m spatial resolution, multispectral IKONOS satellite image of the intertidal habitats of Islesboro, Maine, USA with that of an aerial compact airborne spectral imager survey of the same regions captured 4 years earlier. There was 72% agreement between the surveys in spite of the temporal gaps between the images. Accuracy varied by habitat class and the perceived error can be assigned to temporal and definitional issues rather than basic acquisition and analytic protocols. Most of the error can be explained by: (1) inadequacy of training sites, (2) temporal variations and (3) class definitions. We conclude that IKONOS imagery provides sufficient spatial and spectral resolution to map and monitor diverse intertidal habitats as found in the macrotidal Gulf of Maine.